Jim,

In his second post in the thread, Joe123s specifically wrote that it is a speed plane.

So he does need the full throttle gains.
Most tuned silencers; MVVS in particular, have a very wide RPM operating range.
The .40-.49 tuned silencer will, as it comes, boosts performance in the 10,000-16,000 RPM range, which covers each and every prop you are likely to use with these engines. With the Bolly 11.5x6 I use, you can clearly hear the engine get on-the-mini-pipe at half throttle (not half RPM, though).

A Mac's OS.46FX, ready-to-use, full length pipe, will only be at its best with 10x6 and 10x7 props and with 10-15% nitro fuel.
Change anything and you could be out of the pipe's RPM range.

The Bolly pipe mentioned in the ST test, was to show that this pipe allows the engine to make the same HP at 20% lower RPM.